We are studying mechanisms of virus assembly, with emphasis on the identification of the genes, precursor proteins, and organized intermediates in bacteriophage morphogenesis. The experiments take advantage of the unusually complete genetic characterization of T4, lambda, and P22: By analyzing proteins and structures accumulating in cells infected with amber and temperature sensitive mutants blocked in phage assembly, we can delineate phage head and tail morphogenetic pathways. The analysis employs a variety of techniques including gel electrophoresis, electron microscopy, sedimentation analysis, and in vitro complementation assays. To understand the genetic control of virus assembly we are investigating: 1. Head Assembly and DNA Packaging in Phage P22; Having worked out the overall pathway for P22 head assembly, we intend to focus on the initiation, assembly, and structure of precursor shells in head formation, and on the mechanism of DNA encapsulation and cutting. We have identified a scaffolding protein present in precursor heads, but removed intact during DNA packaging. We will investigate this process further, using the above techniques, and by trying to set up a system in which head assembly proceeds in vitro. 2. Assembly of the Tails of Bacteriophages T4 and Lambda; By defining each gene, protein, and step in phage tail assembly, we can study the control of macromolecular assembly in great detail. Of particular interest; formation of the complex T4 baseplate from its 12 species of precursor proteins; tail length determination; the form of precursor structural proteins; the control of the sequential nature of tail morphogenesis. 3. Protein Folding and the nature of Temperature Sensitive Mutations; By characterizing the inactive proteins which form upon infection with temperature sensitive mutants we hope to identify steps in the folding and maturation of structural proteins.